|ADAMS, SEAN - UNIVERSITY OF CALIFORNIA|
|CARDONA, CAROL - UNIVERSITY OF CALIFORNIA|
|TO, THANH LONG - NATIONAL CENTER FOR VETERINARY DIAGNOSTICS|
|NGUYEN, TUNG - NATIONAL CENTER FOR VETERINARY DIAGNOSTICS|
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2012
Publication Date: 9/25/2012
Citation: Cagle, C.A., Wasilenko, J.L., Adams, S., Cardona, C., To, T., Nguyen, T., Spackman, E., Suarez, D.L., Smith, D.M., Shepherd, E.M., Roth, J.P., Pantin Jackwood, M.J. 2012. Differences in pathogenicity, response to vaccination, and innate immune responses in different types of ducks infected with a virulent H5N1 highly pathogenic avian influenza virus from Vietnam. Avian Diseases. 56:479-487.
Interpretive Summary: The ability of H5N1 highly pathogenic avian influenza (HPAI) viruses to cause disease in wild and domestic waterfowl is poorly understood. Wild ducks are considered reservoirs of avian influenza viruses in nature, and usually don’t show signs of disease. However, some H5N1 HPAI viruses can cause disease and death in both wild and domestic ducks. This study was carried out to compare the clinical disease induced by H5N1 HPAI virus infection among three types of ducks, two domestic (Pekin and Muscovy), and one wild type (Mallard). We also compared the response to vaccination between Pekin and Muscovy ducks. Clear differences were observed in clinical disease after virus infection between the different types of ducks, and also in response to vaccination and innate immune responses. These results should be taken into account when developing effective vaccination programs for controlling HPAI in different species of ducks, since we demonstrated that not all duck species have the same susceptibility to infection and respond equally to avian influenza vaccination.
Technical Abstract: Wild ducks are reservoirs of avian influenza viruses in nature, and usually don’t show signs of disease. However, some Asian lineage H5N1 highly pathogenic avian influenza (HPAI) viruses can cause disease and death in both wild and domestic ducks. The objective of this study was to compare the clinical disease and innate immune responses after infection with a virulent strain of H5N1 HPAI virus among three types of ducks, two domestic (Pekin and Muscovy), and one wild type (Mallard). Response to vaccination was also compared between the Pekin and Muscovy ducks. Differences in response to infection were observed between the virus-challenged Muscovy ducks and the Pekin and Mallard ducks, with the Muscovy ducks dying two days earlier and presenting more severe neurological signs. On the other hand, Pekin and Mallard ducks had significantly higher body temperatures at 2 days post-challenge than Muscovy ducks, indicating possible differences in innate immune responses. Muscovy ducks also exhibited a poorer response to vaccination than Pekin ducks, developing lower viral antibody titers induced by vaccination and presenting with higher morbidity, mortality, and shedding more virus after challenge with the H5N1 HPAI virus. Comparison of the expression of innate immune related genes in spleens of the challenged Pekin, Muscovy and Mallard ducks, showed differences including significantly higher levels of expression of IL6, IL18 and chemokine MIP3b in Muscovy ducks. All three duck species showed similar up-regulation of IFN' and RIG1, and a down-regulation of MHCII. In conclusion, infection with H5N1 HPAI virus produced a similar systemic infection with high mortality in all three duck species; however, infection appeared to be more severe in Muscovy ducks, which in addition, also mounted a poorer immune response to vaccination. The differences in response to virus infection and vaccination can be explained in part by the differences observed in the innate immune responses between the different types of duck examined.